Improvement in steam-boiler flue-joints



ADDISON c. FLETCHERQ? Improvement in Steam Boiler Flue J i Patented Oct. 31,1871.

No l20,508.

Whzamem 2 UNITED STATES PATENT QFFICE.

ADDISON G. FLETCHER, OF NEW YORK, N. Y.

IMPROVEMENT lN STEAM-BOILER FLUE-JOINTS.

Specification forming part of Letters Patent No. 120,508, dated October 31, 1871.

1'0 all whom it may concern:

Be it known that I, ADDISON O. FLETCHER, of the city, county, and State of New York, have invented a new and Improved Flue-Foot for Steam-Boiler Tubes; and I do hereby declare that the following is a full, clear, and exact description of the same, reference being had to the accompanying drawing forming part of this specification.

The object of this invention is to obtain a more active circulation of water at the connections of the tube-fines with the tube-sheet of a boiler, and to more effectively use the heat of the flame and gases at their entrance to the fiues or tubes, by retarding the circulation at the mouths of the tubes, and thereby to obtain a more rapid generation of steam in the portions of the boiler surrounding the tube connections, which are exposed to the most intense heat. The invention also provides both for the better securing of the tubes and their more easy removal and replacement. It consists in a tube-foot of hollow annular construction arranged so that its annular cavity projects outward beyond the outer surface of the tube-sheet and presents itself between the exterior of the tube and the interior of the hole provided in the tube-sheet for its reception.

Figure 1 is a central section of a portion of the tubes of a boiler and surrounding portion of the tube-sheet, and of the connecting tube-foot. Fig. 2 is an outside face view, and Fig. 3 an inside face view with a transverse section of the tube, corresponding with Fig. 1.

Similar letters of reference indicate correspol 1ding parts in the several figures.

A is the tube, and B the tubesheet. The hole a provided in the sheet is considerably larger than the exterior of the tube, (say of about twice its diameter.) C is the flue-foot, made of malleable cast-iron or other suitable metal, of hollow annular form, its annular cavity, 1), being open at the end which comes toward the interior of the boiler to form a water-space. It has in its interior a female-screw thread, 0, into which is tightly screwed a male-screw thread on the exterior of the end of the tube; and it has out upon the inner end of its exterior a male-screw thread, (I, which just passes freely the hole min the tubesheet, and in front of this male-screw thread is a plain cylindrical portion, which fits into the hole a, with a shoulder, e, which abuts against the exterior of the tube-sheet, and enables the flue-foot to be firmly secured in the tube-sheet by a nut, E, screwed onto the thread d inside of the boiler, a gasket, f, of India rubber or other packing material, and a metal washer, g, being applied between the nut and the tube-sheet with the gasket next the tubesheet, to make a steamtight and water-tight joint between the tubesheet and flue-foot. The fluefoot thus secured presents its annular cavity outside of the outer face of the tube-sheet, and its outer end is preferably made of convex rounded form.

This flue-foot is more especially intended to be applied at the ends of the fines or tubes in the tube-sheet nearest the fire which are exposed to the greatest heat. The portions of the fluefoot which project beyond the outer face of the tube-sheet are subject to a very intense heat, and steam is thereby generated very rapidly within their annular water-spaces b, and hence a very active circulation is kept up around the ends of the tubes, while at the same time the soprojecting portions of the tube-foot have the effect of somewhat retarding the ingress of the flame and heated gases to the tubes, and cansin g them to remain longer in contact therewith than they do at the entrances to tubes applied in the usual way, so as to yield a greater portion of their heat at those points where the circulation is so active; and the consequence of this accelera-ted circulation of water and retardation of the flame and gases is that a more rapid generation of steam there takes place. The active circulation also prevents incrustation at the tubejoint.

The invention is applicable, though not, perhaps, with the same amount of adval'itage, at the ends of the tubes furthest from the fire. It is applicable to vertical as well as to horizontal tubular boilers.

lVhat I claim as my invention, and desire to secure by Letters Patent, is-

1. The tube-foot of hollow annular construction, substantially as herein described, whereby it forms at the connection which it makes between the tube and tube-sheet an annular space around the end of the tube.

2. The projection of the annular water-space b of the flue-foot beyond the outer face of the tube-sheet, substantially as herein described.

ADDISON G. FLETCHER.

WVitnesses:

FRED. HAYNES,

R. E. RAJBEAU. 14s 

